DUBAI: Qatar must do more to protect construction workers from heat which often reaches levels that are potentially fatal, Human Rights Watch said Wednesday.

HRW and other rights campaigners are frequent critics of Qatar's treatment of migrant labourers whose working conditions have received additional scrutiny as the country prepares to host the 2022 World Cup.

The group said existing regulations only set limits on outdoor work during the period June 15 to Aug. 31, and then only from 11:30 a.m. to 3 p.m.

"Climate data shows that weather conditions in Qatar outside those hours and dates frequently reach levels that can result in potentially fatal heat-related illnesses in the absence of appropriate rest," it said.

HRW called authorities also to investigate the causes of migrant worker deaths and publish data on such incidents. In 2013, health authorities reported 520 deaths of workers from Bangladesh, India, and Nepal, HRW said.

Like other wealthy Gulf Arab states, Qatar relies on vast numbers of migrant workers, mostly from the Philippines, South Asia and Africa.

Around 2 million migrant workers live in Qatar, outnumbering the local workforce by nearly 20 to one. Some 800,000 work in the construction sector.

Unions and labour protests are banned and authorities penalise dissent with jail or deportation.

The Qatari government's Communications Office said: "Qatar is committed to its labour reform programme and is constantly reviewing its policies to ensure that migrant workers receive the necessary on-site protections.

"We continue to coordinate closely with the International Labour Organisation (ILO) and international NGOs to implement reforms that will improve the health, safety and rights of migrant workers," Sheikh Saif Al Thani, head of the Communications Office, said in a statement sent to Reuters.